|Publication number||US7576429 B2|
|Application number||US 11/364,399|
|Publication date||Aug 18, 2009|
|Filing date||Feb 28, 2006|
|Priority date||Dec 30, 2005|
|Also published as||DE112006003599T5, US7816178, US20070161151, US20090269885, WO2007079399A2, WO2007079399A3|
|Publication number||11364399, 364399, US 7576429 B2, US 7576429B2, US-B2-7576429, US7576429 B2, US7576429B2|
|Inventors||Ruben P. Madrid, Romel N. Manatad|
|Original Assignee||Fairchild Semiconductor Corporation|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (8), Non-Patent Citations (1), Referenced by (7), Classifications (26), Legal Events (3)|
|External Links: USPTO, USPTO Assignment, Espacenet|
This application claims the benefit of U.S. Provisional Patent Application No. 60/755,241 filed Dec. 30, 2005.
Semiconductor devices are used in many consumer electronic products such as cell phones and laptop computers. However, before use the semiconductor must be designed such that they conform to the space allotted in the product in which they are used, as well as deal with other issues arising from the operation of the device itself.
First, it is desirable to remove heat from the semiconductor die while it is in operation, since the die will generate heat during operation. Heat dissipation is desirable because heat can lower efficacy of the die or even fatally affect the device. Thermal clips have been attached to semiconductor dies to act as a natural heat sink, however improved methods of dissipating heat or cooling the die are desirable.
Second, versatility in attachment to printed board circuits is desired. Since consumer products are becoming smaller in size the need for versatility in semiconductors is greater. Creation of packaged semiconductor devices having reversible mounting capabilities to printed circuit boards (PCBs) is desirable. Further, packaged semiconductor devices with the same footprint, which can incorporate differing die sizes or multiple dies, are desirable. Electronic products can vary in the degree of capabilities, requiring different semiconductor dies or even multiple dies but with the same footprint for manufacturing. Thus, a packaged device that allows for differing die sizes or multiple dies with the same footprint is desired. The invention addresses the aforementioned problems as well as others, in separate embodiments collectively and separately.
The embodiments of the invention are directed to a packaged semiconductor device and a method for making the packaged device.
The invention is directed to a semiconductor device comprising: (a) at least one semiconductor die comprising a first surface, a second surface, and a vertical transistor with at least one control region and at least one first terminal region at said first surface, and a second terminal region at said second surface; (b) a thermal clip with a first surface and a second surface wherein said second surface is connected to said drain region of said semiconductor die; (c) at least one first terminal pad structure with a first surface, a second surface, and at least one source lead extending from one side of said first terminal pad structure, wherein said first terminal region of said semiconductor die is connected to said first surface of said first terminal pad structure; (d) at least one control pad structure with a first surface, a second surface, and at least one control lead extending from one end of said control pad structure, wherein said control region of said semiconductor die is connected to said first surface of said control pad structure; (e) at least one second terminal pad structure with a first surface, a second surface, and at least one second terminal lead extending from one end of said second terminal pad structure, wherein said first surface of said second terminal pad is connected to said second surface of said thermal clip; and (f) a nonconductive molding material encapsulating said semiconductor die, wherein said first surface of said thermal clip and said second surface of said first terminal pad structure are exposed through said nonconductive molding material, and wherein said control lead, said first terminal lead and said second terminal lead are exposed through said nonconductive molding material.
The first embodiment includes a mosfet. The embodiment includes a top-exposed thermal clip and a bottom-exposed source pad with one semiconductor die having one gate, source and drain region oriented so that the regions of the semiconductor die are in contact with the corresponding structure (e.g. the source region of the die is attached to the source pad). Further, the source, gate and drain leads are all coplanar with the bottom-exposed source pad.
The second embodiment is similar to the first embodiment, but with a top-exposed source pad and bottom-exposed thermal clip wherein the source, gate and drain leads are all coplanar with the thermal clip.
The third embodiment, again having a mosfet, of the device contains a semiconductor die having two source regions and two gate regions. Therefore, there is a need for two source pads, being top-exposed and two gate pads attached to the appropriate regions of the die. The gate, source and drain leads are all coplanar with the bottom-exposed thermal clip.
The fourth embodiment of the device is a top-exposed thermal clip with a semiconductor die having two source and gate regions, thereby requiring two source and gate pads for attachment to the die. The source, gate and drain leads of this embodiment are coplanar with the bottom-exposed source pads.
All of these embodiments are packaged with a nonconductive molding material encapsulating the semiconductor device to protect it from outside contaminants and environmental factors. These embodiments are not exhaustive of the embodiments of the packaged device. It is possible to use multiple semiconductor dies in this invention. Further, it is possible for the transistor to be a bipolar vertical transistor. The constant feature, however, of this is device is a footprint, comprised of: (1) the control and first terminal leads, (2) either a thermal clip or first terminal pad that is bottom-exposed, and (3) second terminal leads.
The invention is also directed to the method of making these devices, comprising: (a) providing at least one semiconductor die comprising a first surface, a second surface, and a vertical transistor having at least one control region and at least one first terminal region at said first surface and a second terminal region at said second surface; (b) providing a thermal clip with a first surface and a second surface; (c) providing a lead frame array in matrix format, said lead frame comprising at least one first terminal pad structure with at least one first terminal lead extending from one side of said first terminal pad structure; at least one control pad structure with at least one control lead extending from one end of said control pad structure; at least one second terminal pad structure with at least one second terminal lead extending from one end of said second terminal pad structure, wherein said lead frame has a first surface and a second surface; (d) providing a nonconductive molding material; (e) attaching said second terminal region of said semiconductor die to said second surface of said thermal clip; (f) attaching said control region of said semiconductor die to said first surface of said control pad structure and said first terminal region to said first surface of said first terminal pad structure in said lead frame; (g) attaching said second surface of said thermal clip to said first surface of said second terminal pad structure in said lead frame; and (h) encapsulating said semiconductor die, said thermal clip and said lead frame with said nonconductive molding material, wherein said first surface of said thermal clip and said first terminal pad structure on said second surface of said lead frame and said control lead, said first terminal leads and said second terminal leads are exposed through the molding material.
The invention has a number of advantages over the prior art. First, the invention expects high thermal capacity because both sides of the packaged semiconductor device are exposed. Exposure of the thermal clip provides for a natural heat sink in the packaged device. Exposing both the thermal clip and source pad allows the semiconductor to cool naturally while it is in operation, providing for improved thermal capacity. Second, both sides of the packaged device can be attached to a PCB. Third, the packaged semiconductor can incorporate different sized semiconductor dies or even multiple dies and still have the same footprint. Fourth, the manufacturing process of the device is simpler in that pre-plated lead frames may be used, as opposed to plating the lead frames during manufacturing. Lastly, the device is flexible to both copper bumping and electroless nickel gold bumps.
The invention is directed to a packaged semiconductor device. The device includes a semiconductor die, such as a flip chip, having one surface with at least one gate and source region and on the opposing surface a drain region. The semiconductor die may have protrusions on the source/gate surface which couples the flip chip to a surface of a die attach pad in a lead frame or more specifically to the source and gate pads. The drain region of the flip chip is attached to one surface of the thermal clip. The device can either have a top-exposed or thermal clip or source pad, and will have a bottom-exposed source pad or thermal clip, respectively. This assembled device is then covered by a non-conductive molding material, such as plastic resin. The molding material is necessary to protect the flip chip from contaminants or other factors within its environment and also electrically isolates certain parts within the device (e.g. the gate pad from the source pad). However, the gate, source and drain leads are exposed through the molding material as are the external surfaces of the source pad and thermal clip whether they are top or bottom exposed. The leads are coplanar with the bottom-exposed surface whether it is a source pad or thermal clip.
There are several advantages of the packaged semiconductor device. The exposure of the thermal clip and the source pad provides for high thermal capacity, which provides for a cooling mechanism for the die while it is operating. Also, the invention can have embodiments with different size semiconductor dies or multiple dies, and still have the same footprint. Accommodations can be made for the type or quantity of semiconductor dies without sacrificing the package shape, and thus allowing for conformity in the manufacture of the end product in which the packaged semiconductor is used. Further, this invention is comparable in shape to 8-pin small outline package (Std S08) and loss free package (FLPAK) devices.
Looking inward from the cut-away view in
Further, a tie bar 107 is protruding from the source pad 108. The tie bar 107 connects the source pad to the lead frame. Generally, the lead frame is utilized in manufacturing. The lead frame houses the source, gate and drain leads and pads or a die attach pad and leads. These lead frames are in an array format where they are all interconnected by tie rails. The tie rails run parallel to each other with the die attach pad and leads, for instance, between the two tie rails, supported by tie bars. The tie bars support the die attach pad during manufacturing, and attach the die attach pad, which is suspended in the middle, to the tie rails. Once the semiconductor dies are attached to the die attach pad in the lead frame and molding is applied to the lead frame, they can then be cut into individual pieces or punched out of the lead frame, thus leaving a packaged semiconductor device. In this instance, the tie bars 107 support the source pad 108 during assembly.
In a second embodiment,
After the reflow process, the device is then packaged by applying a nonconductive molding material to encapsulate the device, leaving the thermal clip, source pad, and gate, source and drain leads exposed through the molding material (Step 506). Methods of molding the device are known to one skilled in the art. The packaged device can then be marked (Step 507). After marking the device, it is trimmed and formed (Step 508). The device is then singulated by any method known in the art, such as sawing, whereby the gate, source and drain pads are all disconnected from the lead frame array and the tie bars are cut from the tie rails connecting the lead frame arrays (Step 509). The resulting product is a packaged semiconductor device with dual exposed surfaces and leads coplanar with the bottom-exposed surface.
The foregoing embodiments have been described in connection with a vertical mosfet transistor. However those skilled in the art understand that other transistors and devices may be substituted. For example, a vertical bipolar transistor could be substituted for the mosfet with emitter regions and contacts corresponding to the source regions and contacts, a base region and contact corresponding to the gate region and contacts, and a collector region and contact corresponding to the drain region and drain contact.
While the invention has been described with reference to preferred embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof to adapt to particular situations without departing from the scope of the invention. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope and spirit of the appended claims.
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|U.S. Classification||257/718, 257/696, 257/726, 257/727, 257/678, 257/692|
|Cooperative Classification||H01L2924/181, H01L2224/40245, H01L2924/1305, H01L2924/1306, H01L2224/16245, H01L2224/73253, H01L2924/01006, H01L2924/01029, H01L2924/01033, H01L2924/01079, H01L2924/01082, H01L2924/13091, H01L23/49562, H01L2924/01005, H01L2924/01078, H01L24/40, H01L23/4334, H01L2224/17051, H01L24/17|
|Jun 26, 2008||AS||Assignment|
Owner name: FAIRCHILD SEMICONDUCTOR CORPORATION, MAINE
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:MADRID, RUBEN P.;MANATAD, ROMEL N.;REEL/FRAME:021154/0788
Effective date: 20060503
|Sep 7, 2010||CC||Certificate of correction|
|Feb 19, 2013||FPAY||Fee payment|
Year of fee payment: 4